Self healing is one of the prominent features of an SDH network. Self healing means that when the network fails (for example, the fiber is cut), the network discovers a substitute transmission route automatically in a very short time (within 50 ms, as specified by the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T)), and sets up communications again through the substitute transmission route. In this way, the service recovers from the failure automatically, and the user hardly perceives the network failure. The substitute route may use a standby device or use redundancy capabilities of an existing device to recover all services or the services of a specified priority.
The self healing function of the SDH network is implemented through APS. In the existing application, APS is implemented through two system configurations, namely, (1) an interface board, a main control board, and a cross-connect board are configured in the system, and the main control board implements APS protocol processing; or (2) only an interface board and a cross-connect board are configured in the system, and the cross-connect board implements the APS protocol processing. In the foregoing application solution, APS needs to be implemented through a main control board or cross-connect board. Nowadays, the modern communication technologies are developing rapidly, and more and more communication devices need to access an optical network for transmitting services. Most of such devices lack a dedicated main control board or cross-connect board, and are unable to implement APS of optical interfaces based on the foregoing solution.
On the other hand, for most of the communication devices that need to access the optical network, an active board and a standby board coexist. Based on that, an APS solution based on the active board and the standby board is provided in the prior art. In this solution, after a line failure is detected, complete switchover occurs between the active board and the standby board, and complete switchover involves not only port switching but also switching of service processing. In the switchover process, plenty of last words and service information need to be processed. Therefore, the switchover is slow (the switchover time is generally more than one second) in this solution.